Sterilizing grade filters for small scale gas lines, air venting, and liquid applications in the pharmaceutical industry are well known. Typical applications include the sterile venting and filtration associated with tanks, flasks, bottles, and flexible bio-reactors. Known filters that provide bacterial filtration typically employ one or more fluoropolymer membranes and are in the form of membrane disks attached to a plastic filter casing or a capsule. In order to improve flow rate, attempts were made to use thinner membranes for bacterial retention. However, such thin membranes, although highly retentive, typically require the use of at least one protective layer to enable integration into a filtration device, such as a capsule or casing. Achieving an integral filtration article with an adequate seal using dissimilar layers is problematic due to incomplete penetration of the sealant through the entire cross section of all the filtration layers.
As it is desirable to improve the flow rate per unit area of filtration without compromising bacterial retention characteristics, there remains a need for a composite filtration structure that achieves integration into a filtration article, is small in size, is lightweight, and which provides high flow rate per unit area while meeting the bacterial retention requirements of a sterilizing grade filter.